Saturday, July 21, 2012

Active Sand Abrasion in the Northern Polar Region of Mars

The large dune field which surrounds Mars' North Polar cap is actively being modified by the wind, with dunes moving at rates of a meter or more per year (PDF). This new HiRISE image shows that the blowing sand is also abrading the ice-rich ground over which the dunes migrate.

Clearly visible in the black and white and color HiRISE frames is a linear texture on the interdune surface that is oriented north-northeast to south-southwest. This orientation matches that of the horns and slipfaces of the barchan dunes, which together indicate migration from the north-northeast to the south-southwest. Visible here are four zoomed views that provide details of this texture. Zoom A/blue box shows a typical barchan dune. The linear texture is visible, albeit subtly, on the surrounding ground surface.

The texture is more apparent in the next views: A zoom of an interdune surface (Zoom B/red box) shows the wind-etched topography as a series topographic high and lows, with the directional trend indicated by the white arrows. This is also clearly seen next to another dune (Zoom C/yellow box). Further zooming in shows that the topographic highs contain boulders, which may be ice rich (Zoom D/orange box). Most of the sand abrasion probably occurs within the topographic troughs, accentuating topography and abrading away boulders, leaving remnant rocks on the highs. This shows that sand abrasion is actively modifying the surface in Mars' northern latitudes.

This is a stereo pair with ESP_027248_2550.

Photo credit: NASA/JPL/University of Arizona

No comments: